U.S. patent number 4,390,285 [Application Number 06/292,213] was granted by the patent office on 1983-06-28 for method and apparatus for mixing solids with liquids, in particular for gluing wood chips.
This patent grant is currently assigned to Draiswerke GmbH. Invention is credited to Werner Christen, Herbert Durr, Helmut Muller.
United States Patent |
4,390,285 |
Durr , et al. |
June 28, 1983 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for mixing solids with liquids, in particular
for gluing wood chips
Abstract
A system for mixing of wood chips or the like with glue which
involves an intensive movement of the chips during the addition of
the glue and a subsequent thorough mixing of the glue and the chips
in a ring of material to be mixed, is characterized by steadily
accelerating the chips out of an axial motion via a centrifugal and
helical motion and by the addition of the glue during this
acceleration, the acceleration to the velocity of the ring of
material to be mixed taking place only following the addition of
the liquid.
Inventors: |
Durr; Herbert (Viernheim,
DE), Christen; Werner (Mannheim, DE),
Muller; Helmut (Mannheim, DE) |
Assignee: |
Draiswerke GmbH (Mannheim,
DE)
|
Family
ID: |
27188841 |
Appl.
No.: |
06/292,213 |
Filed: |
August 12, 1981 |
Foreign Application Priority Data
|
|
|
|
|
Aug 24, 1980 [DE] |
|
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3032039 |
Sep 26, 1980 [DE] |
|
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3036346 |
Feb 16, 1981 [DE] |
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3105549 |
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Current U.S.
Class: |
366/170.3;
366/102; 366/147; 366/149; 366/170.4; 366/172.1; 366/192;
366/329.1; 366/330.1 |
Current CPC
Class: |
B01F
7/022 (20130101); B01F 15/0254 (20130101); B27N
1/0245 (20130101); B01F 15/068 (20130101); B01F
15/065 (20130101); B01F 7/0025 (20130101); B01F
2003/1257 (20130101); B01F 2015/061 (20130101) |
Current International
Class: |
B01F
15/06 (20060101); B01F 7/02 (20060101); B01F
15/00 (20060101); B27N 1/02 (20060101); B27N
1/00 (20060101); B01F 7/00 (20060101); B01F
3/12 (20060101); B01F 005/04 (); B01F 007/04 () |
Field of
Search: |
;366/154,155,165,167,168,172,173,156,157,177,40,33,30,101,102,106,107,150 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jenkins; Robert W.
Attorney, Agent or Firm: Browdy and Neimark
Claims
What is claimed is:
1. A method for mixing of particulate solids with liquids, in
particular for gluing wood chips or the like, wherein there is an
intensive movement of the solids during the addition of the liquid
and a subsequent thorough mixing of the liquid and the solids in a
ring of material to be mixed, characterized in that the solids are
steadily accelerated out of an axial motion via a centrifugal and
helical motion and the addition of liquid is effected during this
acceleration, and that the acceleration to the velocity of the ring
of material to be mixed takes place only following the addition of
the liquid.
2. A method as defined by claim 1, characterized in that the solids
are spread apart conically during the acceleration.
3. A method as defined by claim 1, characterized in that the liquid
is sprayed into the solids with air as a carrier means for the
liquid.
4. A method as defined by claim 1, characterized in that the liquid
is supplied to the solids from the outside in the form of a mist
sprayed in approximately disclike fashion.
5. A method as defined by claim 4, characterized in that the liquid
is accelerated within a gap rotating at high speed and having an
approximately annular disclike form.
6. An apparatus for performing the method as defined by claim 1,
having a mixing vessel in which a mixing shaft capable of being
driven at high speed and equipped with mixing tools is disposed,
which vessel is provided at one end, in the vicinity of an
induction zone for the solids, with a material inlet pipe and at
the other end with a material outlet pipe, and which vessel is
provided in a region following the induction zone with at least one
liquid feed device and has a mixing zone in a further following
region, in which mixing zone the liquid/solids mixture mixed in the
form of a ring of material to be mixed, characterized in that
disposed between the induction zone (A) and the mixing zone is an
acceleration zone (B) formed by a portion (30) of the mixing vessel
(1) which widens in conical fashion in the direction (31) of
passage of the material through the vessel, in which acceleration
zone (B) the radial length of the mixing tools (20') steadily
increases.
7. An apparatus as defined by claim 6, characterized in that the
ratio of the radius (r.sub.29) of the cylindrical portion (29) of
the mixing vessel (1) forming the induction zone (A) to the radius
(r.sub.32) of the cylindrical portion (32) of the mixing vessel
forming the mixing zone (C) amounts to between 0.6 and 0.8 to
1.
8. An apparatus as defined by claim 6, characterized in that the
conical portion (30) of the mixing vessel (1) has an apex angle
(.alpha.) of 8.degree. to 15.degree.. PG,22
9. An apparatus as defined by claim 6, characterized in that the
liquid feed devices (44) are embodied as dual-substance
nozzles.
10. An apparatus as defined by claim 6, characterized in that the
liquid feed device (47) has a gap (51) defined by two rotationally
drivable centrifugal plates (48, 49), the gap being open at its
outer circumference and having an approximately annular-disc-like
form, of narrow width (c), the outer centrifugal plate (49) being
disposed at an immediately adjacent distance from the inner wall of
the mixing vessel (1).
11. An apparatus as defined by claim 10, characterized in that the
distance (c) between the centrifugal plates (48, 49) is
adjustable.
12. An apparatus as defined by claim 10, characterized in that an
electromotor (56) is flanged to the outside of the mixing vessel
(1), with the motor shaft protrusion (66) of which the centrigual
plates (48, 49) are directly connected.
13. An apparatus as defined by claim 10, characterized in that a
locally stationary annular channel (70) for liquid supply
discharges into a liquid chamber (71) embodied at the centrifugal
plates (48, 49) and discharging in the gap (51).
14. An apparatus as defined by claim 10, wherein the outer
centrifugal plate adjacent to the wall of the mixing vessel is
drivable, characterized in that the outer centrifugal plate (49)
has at least one fan blade (75) extending up to the vicinity of the
wall.
Description
FIELD OF THE INVENTION
The invention relates to a method and apparatus for mixing
particulate solids and liquids, especially for mixing liquid glue
and wood chips or the like where there is intensive movement of the
chips while the glue is added and a subsequent thorough mixing of
the glue and the chips in a ring of mixed material. Such an
apparatus has a mixing vessel in which a mixing shaft capable of
being driven at high speed and equipped with mixing tools is
coaxially disposed. The vessel is provided at one end, in the
vicinity of an induction zone, with a material feed funnel and at
the other end with a material outlet funnel. In an area following
the induction zone, the mixing vessel is provided with at least one
glue feed device. A mixing zone in which the glued chips are mixed
in a ring of mixing material is disposed still farther from the
induction zone.
BACKGROUND OF THE INVENTION
Methods and apparatus of this kind are known from German Pat. No.
20 57 594 and from U.S. Pat. No. 3,724,471. These mixers for gluing
wood chips have revolutionized chip gluing, because an extremely
fine distribution of the glue on the surface of the chips took
place in such mixers in a minimum of space and at a maximum
intensity. This produced a significant saving of glue as well as of
plant costs in comparison with previously conventional, high-volume
axial or centrifugal and helical mixers. The mechanism of operation
in these so-called ring mixers is such that the material to be
mixed is accelerated by a mixer driven far faster than critical
speed such that the material moves in a helical pattern, in the
form of a relatively thin ring of material, on the inner wall of
the mixing vessel. The glue is introduced directly into this ring
of material. In the forms of embodiment described in the documents
cited, the glue is introduced through the hollow mixing shaft and
through liquid feed pipes radially extending from the shaft and
dipping into the ring of material to be mixed. In another form of
embodiment, described in German Pat. No. 21 34 305, the glue is
introduced through liquid feed pipes which are fixed in the vessel
wall in a locally stationary manner and pass through the vessel
wall into the interior of the mixing vessel; the outlet openings of
these liquid feed pipes terminate in the ring of material to be
mixed.
Despite the substantial advantages attained in terms of structure,
apparatus and engineering methods by the gluing mixer described
above, the disadvantage remained that a large proportion of the
wood chips was damaged by the extremely large acceleration forces,
which caused an undesirable reduction in the quality of the
particle boards made from such chips.
This was true particularly in the case of inferior woods.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide for
improved mixing of solids and liquids without damage to the solids;
another object of the invention is to create a method of the
general type described above and an apparatus of the general type
described above, wherein damage to the wood chips is precluded to
the greatest possible extent and wherein better distribution of the
glue is attained.
A key feature of the invention is that the acceleration of the
chips is extended over a relatively long period of time, in
comparison with known ring mixers; that is, it takes place
relatively slowly. The forces of acceleration, which could cause
possible damage to the chips, are thereby substantially reduced.
There is thus a continuous acceleration, stretched out over time,
with a transition from an axial mixing motion to an annular mixing
motion by way of an intermediate centrifugal and helical motion.
The introduction of the glue occurs in part still during the axial
mixing movement of the chips and then during the centrifugal and
helical mixing movement of the chips; in other words, even while
the glue is being introduced, it is not necessary to exert any
mechanical forces by way of bottlenecks or the like in order to
distribute the glue among the chips. On the other hand, however,
the addition of glue is followed by the advantageous, highly
intensive distribution of glue on the surface of the chips in a
ring of material being mixed. The conical widening of the mixing
vessel in the acceleration zone furnishes the necessarily enlarged
volume of space in which the chips are able to spread out from the
relatively dense packet characterizing the axial mixing phase to a
less-dense volume characterizing the centrifugal and helical mixing
phase. Subsequent to this, a sufficiently large radius of the
mixing vessel is again available in the mixing zone; this is of
course necessary so that the tangential accelerations required for
the formation of the ring of mixing material will be generated.
Again, the manner of glue feeding the acceleration zone makes it
possible to use the known means of glue feeding by means of
pressure nozzles; this has the substantial advantage that the glue
can be used with a smaller proportion of water than was previously
conventional. The previously conventional ratio of dry glue
compound to water was 1:1. This reduction of the water content
means that the water content of the wood chips can be
correspondingly higher; the drying of the wood chips, which is
associated with high energy consumption, can thus be terminated
somewhat earlier than has previously been possible.
Numerous further advantages and features of the invention will be
more apparent from the following detailed description of two
exemplary embodiments taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a mixer in accordance with the invention in vertical
lengthwise section;
FIG. 2 shows a modified mixer in accordance with the invention in
partial lengthwise section;
FIG. 3 shows a cross-section of the mixer according to FIGS. 1 and
2 along the line III--III in FIGS. 1 and 2;
FIG. 4 shows a cross-section in accordance with FIG. 2 of a
modified mixer;
FIG. 5 shows a further mixer in accordance with the invention in a
vertical lengthwise section;
FIG. 6 is a cross-section taken through the mixer along the line
VI--VI of FIG. 5; and
FIG. 7 is a cross-section taken through a glue feed device of the
mixer along the line VII--VII of FIG. 5.
Since the mixers shown in the drawings are only different in the
area of the drawings which lies to the right, the mixer shown in
FIG. 2 is depicted as closed in the areas corresponding with FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The mixers each have a mixing vessel 1, which comprises an inner
trough 2 forming the inner wall thereof and a cooling jacket 3
surrounding the inner trough 2 and forming the outer wall. The
mixing vessel 1 is closed at either end by bulkheads 4, 5. At one
end of the mixing vessel 1 (on the right in FIGS. 1 and 2), a
material feed pipe 6 is provided which discharges into the interior
7 of the mixing vessel, which is enclosed by the inner trough 2 and
the bulkheads 4, 5, at a tangent from the top. On the other end (on
the left in FIGS. 1 and 2), a material outlet pipe 8 is provided
which likewise discharges at a tangent from the interior. The
mixing vessel 1 is divided in half along the horizontal plane; the
upper half 9 and the lower half 10 of the mixing vessel 1 are held
together in a manner such that they can be released and swung open
by means of hinges 11 on one long side and toggle lever closures 12
on the opposite long side.
A mixing shaft 13 is disposed coaxially within the mixing vessel 1,
being supported in bearings 14, 15, and is drivable by an
electromotor, not shown, via a V-belt pulley 16 attached in a
rotationally fixed manner to the mixing shaft 13. Load-compensating
plates 17, 18 are also disposed on the mixing shaft 13 outside the
mixing vessel 1 itself but in the vicinity of the bulkheads 4, 5.
Threaded sockets 19 are attached to the mixing shaft 13, and hollow
mixing tools 20 are threadedly inserted into them. A coolant supply
pipe 21 is disposed within the mixing shaft 13 and rotates with it;
a coolant pipe 22 branches off from the supply pipe 21 into each
hollow mixing tool 20, so that the coolant flows through the
coolant supply pipe 21, the branching coolant pipes 22 and the
interior of each mixing tool 20 into the annular chamber 23 located
between the coolant supply pipe 21 and the mixing shaft 13. The
coolant reaches the interior of the mixing shaft 13 via a coolant
pipe coupling 24 (provided on the right in FIGS. 1 and 2); the
inflow into the coolant supply pipe 21 is indicated by arrow a, and
the coolant outflow from the annular chamber 23 is in the direction
indicated by arrow b. The bearings 14, 15 are mounted on bearing
bases 25, 26.
The region of the mixing vessel 1 over which the material feed pipe
6 extends in the longitudinal direction of the mixing vessel 1 is
embodied in cylindrical form and creates an induction zone A for
the material to be mixed, conventionally wood chips. So-called
induction tools are attached to the mixing shaft 13 in this
induction zone A; in the case of the exemplary embodiment shown in
FIG. 1, the induction tools 27 are vanelike in embodiment, while in
the exemplary embodiment shown in FIG. 2, there is a helical
induction tool 28. The induction tools 27 or 28 serve to propel the
mixing material falling through the material feed pipe 6 into this
cylindrical portion 29 of the mixing vessel 1 in a primarily
axially directed movement into the next adjacent, conically
embodied portion of the mixing vessel. This portion 30, which
widens in conical or more specifically frustoconical fashion in the
direction 31 in which material passes through the vessel 1, forms
an acceleration zone B for the material to be mixed. This conical
portion 30 is followed by a portion 32 of the mixing vessel 1 which
is again cylindrical; this portion 32 forms a mixing zone C
extending up to the material outlet pipe 8 and an expulsion zone D
extending over the axial length of the material outlet pipe 8. The
conical portion 30 widens from radius r.sub.29 to radius r.sub.32
of the cylindrical portion 32. The ratio of the radii r.sub.29 to
r.sub.32 amounts to between 0.6 and 0.8 to 1 and is preferably 0.75
to 1.
The apex angle .alpha. of the conical portion 20 is approximately
8.degree. to 15.degree. and preferably approximately 10.degree..
The axial length of acceleration zone B has a ratio to mixing zone
C of approximately 1:2. In accordance with the conical path of the
inner wall of the mixing vessel 1 in the conical portion 30, the
mixing tools in this region have a substantially shorter radial
length than in the cylindrical portion 32. For this reason, the
mixing tools in this acceleration zone B are provided with
reference numeral 20'; the radial length of these mixing tools 20'
increases steadily from the beginning of the acceleration zone B
(that is, from the end of the induction zone A) to the end of the
acceleration zone B (that is, to the beginning of the mixing zone
C), as may be seen in the drawing.
Liquid feed pipes 33 (FIG. 1) or 34 (FIG. 2) intended particularly
for adding glue to wood chips discharge into the acceleration zone
B. In the form of embodiment shown in FIG. 1, the liquid feed pipes
33 terminate approximately at the inner wall, formed by the inner
trough 2, of the conical portion 30 of the mixing vessel 1. The
liquid can be supplied to these feed pipes either unpressurized, as
is conventional and as is described in U.S. Pat. No. 4,183,676, or
under pressure. In the latter case, atomizer nozzles 35 are
disposed on the inner ends of the liquid feed pipes 33, in the
manner described in U.S. Pat. No. 3,163,403, for example. As may be
seen in FIG. 1, the liquid feed pipes 33 are disposed substantially
in the forward section (with respect to the induction zone A) of
the acceleration zone B.
In the form of embodiment shown in FIG. 2, the liquid feed pipes 34
protrude to varying extents into the interior 7 of the mixing
vessel 1; the first liquid feed pipe 34', seen again from the
induction zone A and looking in the material passage direction 31,
extends the farthest away from the inner wall radially into the
interior, while the next liquid feed pipes 34", 34'" and 34"" in
sequence in the direction 31 of material passage extend
progressively less far from the wall into the interior 7, and the
last liquid feed pipe 34"" terminates approximately at the inner
wall itself. As in the first embodiment, the supply of liquid may
be either not under pressure or under pressure; in each case, the
outlet of the liquid is at the radially inwardly disposed end of
the respective liquid feed pipe 34. In both exemplary embodiments,
the liquid feed pipes 33 or 34 are located in the vertical axial
plane of the mixing vessel 1.
In the exemplary embodiment of FIG. 2, the liquid outlet openings
36 are thus disposed on a line which, with the longitudinal axis 37
of the mixing vessel 1, forms an angle .beta., which in every case
is clearly larger than .alpha.. The angle .beta. measures
approximately 20.degree. to 25.degree..
A throttle valve 38 is disposed on the material outlet pipe 8 in a
conventional manner; it is articulated at its upper, axially
parallel edge by means of hinges 39 on the mixing vessel 1. The
pressure of the material to be mixed moves the throttle valve 38
out of the closed position shown in FIG. 3, pivoting it downward
and to the side as indicated by the arrow 40, so that the material
outlet opening is opened to a greater to lesser extent. The mixing
tools 20, in turn, moving in the rotary direction 41, propel the
material centrifugally out through the mixture outlet opening,
opened to a greater or lesser extent, and into the material outlet
pipe 8. A counterweight 42 which can be adjusted by a motor is
mounted on the outside of the throttle valve 38, as is described in
detail in U.S. patent application Ser. No. 154,098. This
motor-adjustable counterweight serves to augment the possibility
(which exists in any event) that the throttle valve 38 will open in
accordance with the pressure of the material to be mixed in the
mixing vessel 1 with the further possibility of varying the closing
pressure available at every open position of the throttle valve 38
by means of adjusting the counterweight 42.
The mixing of the material with liquid (that is, in particular the
mixing of wood chips and glue) proceeds as follows:
The material introduced through the material inlet pipe 6 is
propelled axially by the induction tools 27 or 28 into the
acceleration zone B in the passage direction 31, undergoing a
relatively slight tangential acceleration. Because of this
predetermined axial propulsion, the material continues to pass
through this zone B in an axial direction. At the same time, the
material is increasingly accelerated tangentially by the mixing
tools 20', so that out of a purely axial mixing movement a
centrifugal mixing movement is brought about, in the course of
which the material (as a rule, wood chips) is propelled
centrifugally and helically over the full cross section of the
mixing vessel in this region. The liquid (as a rule, glue) is
introduced into this centrifugal and helical movement of the
material, being either sprayed in or fed without pressure. In the
manner of feeding shown in FIG. 2, the glue is fed through the
first liquid feed pipe 34', which protrudes deeply into the mixing
vessel 1, into the chips while they are still in the transition
from axial mixing to centrifugal and helical mixing. Through the
subsequent liquid feed pipes 34", 34'" and 34"", the glue is
increasingly added to chips whose motion is more and more
turbulent. Thus the glue is introduced in a region where the wood
chips are steadily brought from a slow axial motion into a
centrifugal and helical motion over a relatively long period of
time; in other words, the transition is not overly abrupt, and the
wood chips are thereby protected from damage. After the glue has
been added, there is a further acceleration of the chips, so that a
ring 43 of material again forms in the mixing zone C on the inner
wall of the mixing vessel in the conventional manner; an intensive,
thorough mixing of the wood chips and the glue takes place in this
ring 43 of material.
The mixing shaft 13 is driven at high speed, so that at least in
mixing zone C the prevailing rpm is far beyond the critical number.
The critical rpm is defined as that at which an acceleration which
equals that due to gravity engages the radially outwardly disposed
ends of the mixing tools 20. In order to be able to exert
corresponding forces of acceleration, the mixing tools 20 and 20'
terminate in the vicinity of the inner wall of the mixing vessel 1.
This is true particularly for the mixing tools 20 disposed in
mixing zone C, because the material ring 43 is of course relatively
thin in this zone, and the mixing tools 20 must protrude into this
material ring 43 in order to be capable of continuously exerting
acceleration forces on the wood chips forming the material ring
43.
Naturally, in the case where liquid or more specifically glue is
added under pressure through the liquid feed pipes, compressed gas
can be used as a supplementary aid to atomization.
Liquid feed nozzles 44 intended in particular for adding glue to
wood chips discharge into the acceleration zone B (see FIG. 4),
terminating close to the inside of the inner trough 2 of the mixing
vessel 1; in other words, they do not protrude into the interior 7
of the mixing vessel 1. As may be seen in FIG. 4, these liquid feed
nozzles 44 discharge substantially at a tangent into the interior
7. They are so-called dual-substance nozzles, by means of which
both liquid glue, supplied by a glue supply line 45, and compressed
air, supplied by a compressed-air line 46, are sprayed into the
interior 7 with the finest possible distribution.
The centrifugal and helical movement of the chips is substantially
reinforced by the air sprayed through the liquid feed nozzles 44.
The air serves not only as a carrier medium for the glue (that is,
as a means of atomizing the glue), but contributes quite
substantially to loosening up of the chips as well.
The compressed air is supplied to the liquid feed nozzles 44 at a
pressure in the range of from 2 to 6 bar, preferably at a pressure
of from 2.5 to 4 bar.
At an average specific weight of the wood chips of 100 kg/m.sup.3,
compressed air is supplied to the liquid feed nozzles 44 at a ratio
of from 2 to 5 Norm m.sup.3 /m.sup.3 of chips; the ratio is
preferably 2.5 to 3.5 Norm m.sup.3 /m.sup.3 of air per m.sup.3 of
chips.
Since the mixer shown in FIGS. 5-7 is identical in its basic design
to that of FIG. 2, it need not be described fully. Comparable parts
are identified by identical reference numerals, with the addition
of a prime.
In the exemplary embodiment shown in FIGS. 5-7, the conical portion
30' widens from radius r.sub.29' to radius r.sub.32' of the
cylindrical portion 32'. The ratio of the radii r.sub.29' to
r.sub.32' is between 0.55 and 0.7 to 1 and preferably approximately
between 0.6 and 0.65 to 1. The conical apex angle .alpha. of the
conical portion 30' is approximately 12.degree. to 20.degree. and
preferably approximately 18.degree.. The ratio of the axial length
of acceleration zone B' to the axial length of mixing zone C' is
approximately 1:2. In accordance with the conical path of the inner
wall of the mixing vessel 1' in the conical portion 30', the mixing
tools here as well are embodied as substantially shorter in radial
length than in the cylindrical portion 32'. For this reason, the
mixing tools present in this acceleration zone B' are identified by
reference numeral 20"; the radial length of these mixing tools 20"
increases approximately steadily from the beginning of the
acceleration zone B' (that is, from the end of the induction zone
A'), up to the end of the acceleration zone B' (that is, up to the
beginning of the mixing zone C', as may be seen from FIG. 5.
In the expulsion zone D', the mixing tools are embodied in
approximately vanelike fashion in order to generate tangential
movements on the part of the material to be mixed, and they are
therefore identified by reference numeral 20'".
In acceleration zone B', which in the illustrated exemplary
embodiment is at the transition from the conical portion 30' to the
cylindrical portion 32', a glue feed device 47 is provided, which
functions centrifugally. It has two centrifugal plates which are
interconnected in a rotationally fixed manner; these are an inner
centrifugal plate 48 and an outer centrifugal plate 49, which
between them define a substantially radial gap 51 relative to the
central longitudinal axis 50 of the glue feed device 47. The outer
centrifugal plate 49, oriented toward the inner wall of the mixing
vessel 1, adjoins a tubular portion 52 in which a likewise tubular
centering portion 53 is fixedly disposed by means of several radial
crosspieces 54. The inner centrifugal plate 48 has a centering
shoulder 55, by means of which it is held both radially and axially
within the tubular centering portion 53. The width c of the gap 51,
which is substantially in the form of an annular plate, may be
varied by provision of an appropriate length of the tubular
centering portion 53 or by means of interposing shims at the joint
between the centering shoulder 55 and the centering portion 53.
A conventional electromotor 56 serves to drive the centrifugal
plates 48, 49; it is screwed on a short support frame 57, which is
screwed in turn on a pipe fitting 58 passing to the outside through
the inner trough 2' and the cooling jacket 3' of the mixing vessel
1'. The inner diameter of the pipe fitting 58 is somewhat larger
than the outer diameter of the tubular portion 52. The support
frame 57 comprises several crosspieces 59, extending parallel to
the axis 50, and annular flanges 60, 61 attached at either end,
which are releasably fastened by means of screws 64 to a
corresponding flange 62 of the pipe fitting 58 and to the
attachment flange 63 of the electromotor 56, respectively.
The centrifugal plates 48, 49 are screwed in a rotationally fixed
manner to the shaft protrusion 66 of the motor 56 by means of a
threaded screw which passes through the centering shoulder 55
coaxially with the axis 50. A spacer 67 is provided, which is
supported axially against the shaft protrusion 66 on one end and on
the other end engages the inside of the centering portion 53. The
centering portion 53 is axially supported via a shoulder 68 against
the spacer 67, so that when the threaded screw 65 is tightened, the
inner centrifugal plate 48 is clamped with its centering portion 53
to the outer centrifugal plate 49 and thus the latter element is
also clamped firmly to the shaft protrusion 66. The centrifugal
plates are thereby fixed axially, while the width c of the gap 51
is fixed at the same time, and the two centrifugal plates are
connected to the shaft protrusion 66 in a rotationally fixed
manner.
An annular plate 69 is secured on the crosspieces 59 in the
vicinity of the annular flange 61 oriented toward the electromotor
56, and an annular-cylindrical channel 70 which is closed in the
direction of the annular plate 59 is screwed onto the plate 69. The
annular-cylindrical channel 70 discharges freely into the glue
chamber 71 between the tubular portion 52 and the centering portion
53. A threaded fitting 72 discharges laterally into the annular
channel 70, and a glue supply line (not shown) may be attached to
the threaded fitting 72.
As may be seen in FIG. 7, the gap 51 does not have an exactly
radial course; instead, it has the form of a truncated cone with a
very large apex angle, that is, a very small base angle .beta. of
approximately 5.degree. to 10.degree., which corresponds to an apex
angle of 170.degree. or 160.degree.. The base angle .beta. may be
selected, by way of example, such that it is equal to .alpha.'/2,
if the glue feed device 47 is disposed at the transition from the
conical portion 30' to the cylindrical portion 32'. In this case,
the glue feed device 47 is disposed such that its longitudinal axis
50 is inclined, with respect to the lengthwise section of the mixer
shown in FIG. 5, at an angle of .alpha.'/2.
The introduction of glue into zone B' is effected in such a manner
that glue is fed in a metered fashion into the annular channel 70
by a pump, not shown, via a glue supply line, also not shown. From
the annular channel 70, the glue flows downward into the glue
chamber 71, as indicated by arrows 73. Particularly on the upper
part of the inner centrifugal plate 48, the glue undergoes strong
radial acceleration and is driven through the gap 51, leaving this
gap in the form of a fine mist having a very high tangential
velocity. The speed of the centrifugal plates is conventionally
2800 rpm; given a diameter for the centrifugal plates 48, 49 of 140
mm, this translates into velocity at the circumference of the
centrifugal plates at the outlet of the gap 51 of somewhat more
than 20 m/sec. The glue is thus distributed extremely finely and at
a very high velocity into the material, that is, into the chips in
particular. A portion of the glue is deposited on the inner wall of
the inner trough 2', particularly in the conical portion 30'. Since
the mixer is well cooled, the inner wall has a relatively low
temperature, so that water condenses on the wall and thins the
deposited glue. This glue can thus be absorbed particularly easily
by the wood chips flowing past it. Since coarse chips or dust is
more likely to be located in the vicinity of the wall rather than
fine chips or dust, these coarse chips are thereby glued relatively
more heavily, which is desirable.
Approximately at the beginning of the mixing zone C', a ring 74 of
mixing material forms on the inner wall of the mixing vessel 1'.
Here, an intensive, thorough mixing of the wood chips and glue
takes place.
As may be seen from FIG. 7, the mixing tools 20" or 20' pass inside
the inner centrifugal plate 48 in the vicinity of the glue feed
device 47. Should the material ring 74 already be taking form in
its initial stages in this region of the mixing vessel 1, then it
would pass near by the inner side of the inner centrifugal plate
48. Because of the fact that the outer centrifugal plate 49 is
driven at high speed, no chips are able to get into the space
between the inner wall of the inner trough 2' and the centrifugal
plate 49, which is only a few millimeters wide. If such a ring is
already partially forming, then the mist of glue is applied from
the outside onto this material ring.
The glue feed device 47 may be supplied with glue without pressure;
as a result, a particularly precise metering of glue is made
possible in a known manner.
It may also be seen from FIG. 7 that the centrifugal plates 48, 49
are tapered in their outer circumference down to the outlet of the
gap, so that as a unit the centrifugal plates have no
annular-cylindrical rim on which material to be mixed (that is,
chips) could back up. The chips are thus able to pass smoothly by
the inner side of the inner centrifugal plate 48.
As may be seen in FIG. 7, a crosspiece-like fan blade 75 may be
disposed on the outer centrifugal plate 49, which improves the
cleaning action of the rotating centrifugal plate 49 with respect
to the inner wall of the inner trough 2'.
It will be obvious to those skilled in the art that various changes
may be made without departing from the scope of the invention, and
the invention is not to be considered limited to what is shown in
the drawings and described in the specification.
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